// This file is part of Deja-Vu.
//
// Deja-Vu is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Deja-Vu is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
// See the GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Deja-Vu. If not, see <https://www.gnu.org/licenses/>.
#![allow(clippy::missing_errors_doc)]
#![allow(clippy::missing_panics_doc)]

use std::{
    collections::VecDeque,
    fmt,
    path::PathBuf,
    process::{Command, Stdio},
    sync::{Arc, Mutex},
    thread::{self, JoinHandle, sleep},
    time::Duration,
};

use color_eyre::Result;
use serde::{Deserialize, Serialize};
use tokio::sync::mpsc;
use tracing::info;

use crate::{
    action::Action,
    components::popup,
    system::{disk, diskpart},
};

#[derive(Clone, Debug)]
pub enum TaskResult {
    Error(String),
    Output(String, String, bool), // stdout, stderr, success
}

#[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
pub enum TaskType {
    CommandNoWait(PathBuf, Vec<String>), // (command, args)
    CommandWait(PathBuf, Vec<String>),   // (command, args)
    Diskpart(String),                    // (script_as_string)
    ScanDisks,
    Sleep,
    TestPaths(Vec<PathBuf>),
    UpdateDestDisk(usize), // (disk_index)
    UpdateDiskList,
}

impl fmt::Display for TaskType {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            TaskType::CommandNoWait(cmd_path, _) | TaskType::CommandWait(cmd_path, _) => {
                write!(
                    f,
                    "Command(\"{}\")",
                    cmd_path.file_name().unwrap().to_string_lossy()
                )
            }
            TaskType::Diskpart(_) => {
                write!(f, "Diskpart")
            }
            TaskType::ScanDisks => write!(f, "ScanDisks"),
            TaskType::Sleep => write!(f, "Sleep"),
            TaskType::TestPaths(_) => write!(f, "TestPaths"),
            TaskType::UpdateDestDisk(_) => write!(f, "UpdateDestDisk"),
            TaskType::UpdateDiskList => write!(f, "UpdateDiskList"),
        }
    }
}

#[derive(Debug)]
pub struct Task {
    pub handle: Option<JoinHandle<()>>,
    pub result: Option<TaskResult>,
    pub task_type: TaskType,
}

impl Task {
    #[must_use]
    pub fn new(task_type: TaskType) -> Task {
        Task {
            handle: None,
            result: None,
            task_type,
        }
    }
}

#[derive(Debug)]
pub struct Tasks {
    action_tx: mpsc::UnboundedSender<Action>,
    disk_list: Arc<Mutex<Vec<disk::Disk>>>,
    cur_handle: Option<JoinHandle<()>>,
    cur_task: Option<Task>,
    task_list: VecDeque<Task>,
    task_rx: mpsc::UnboundedReceiver<TaskResult>,
    task_tx: mpsc::UnboundedSender<TaskResult>,
}

impl Tasks {
    pub fn new(
        action_tx: mpsc::UnboundedSender<Action>,
        disk_list_arc: Arc<Mutex<Vec<disk::Disk>>>,
    ) -> Self {
        let (task_tx, task_rx) = mpsc::unbounded_channel();
        Tasks {
            action_tx,
            disk_list: disk_list_arc,
            cur_handle: None,
            cur_task: None,
            task_list: VecDeque::new(),
            task_rx,
            task_tx,
        }
    }

    pub fn add(&mut self, task_type: TaskType) {
        info!("Adding task: {:?}", &task_type);
        self.task_list.push_back(Task::new(task_type));
    }

    #[must_use]
    pub fn idle(&self) -> bool {
        self.cur_handle.is_none()
    }

    pub fn poll(&mut self) -> Result<Option<Task>> {
        let mut return_task: Option<Task> = None;
        // Handle task channel item(s)
        if let Ok(result) = self.task_rx.try_recv() {
            if let Some(mut task) = self.cur_task.take() {
                task.result.replace(result);
                self.cur_task.replace(task);
            }
        }

        // Check status of current task (if one is running).
        // NOTE: Action::TasksComplete is sent once all tasks are complete
        if let Some(task_handle) = self.cur_handle.take() {
            if task_handle.is_finished() {
                // Need to return task with handle
                if let Some(mut cur_task) = self.cur_task.take() {
                    cur_task.handle = Some(task_handle);
                    return_task = Some(cur_task);
                }
                if self.task_list.is_empty() {
                    // No tasks remain
                    self.action_tx.send(Action::TasksComplete)?;
                } else {
                    // Start next task
                    self.start()?;
                }
            } else {
                // TaskType not complete, return handle
                self.cur_handle.replace(task_handle);
            }
        } else if !self.task_list.is_empty() {
            // No current task but one is available
            self.start()?;
        }
        Ok(return_task)
    }

    pub fn start(&mut self) -> Result<()> {
        self.cur_task = self.task_list.pop_front();
        if let Some(task) = self.cur_task.take() {
            let task_tx = self.task_tx.clone();
            self.action_tx
                .send(Action::TaskStart(task.task_type.clone()))?;
            match task.task_type {
                TaskType::CommandNoWait(ref cmd_path, ref cmd_args) => {
                    self.cur_handle = None;
                    run_task_command(cmd_path.clone(), cmd_args.clone(), task_tx);
                }
                TaskType::CommandWait(ref cmd_path, ref cmd_args) => {
                    self.cur_handle = Some(run_task_command(
                        cmd_path.clone(),
                        cmd_args.clone(),
                        task_tx,
                    ));
                }
                TaskType::Diskpart(ref script) => {
                    self.cur_handle = Some(run_task_diskpart(script, task_tx));
                }
                TaskType::ScanDisks => {
                    let disk_list_arc = self.disk_list.clone();

                    // Queue UpdateDiskList for various components
                    self.add(TaskType::UpdateDiskList);

                    self.cur_handle = Some(thread::spawn(move || {
                        let mut disks = disk_list_arc.lock().unwrap();
                        *disks = disk::get_disks();
                    }));
                }
                TaskType::Sleep => {
                    self.cur_handle = Some(thread::spawn(|| sleep(Duration::from_millis(250))));
                }
                TaskType::TestPaths(ref list) => {
                    self.cur_handle = Some(test_paths(list.clone(), task_tx.clone()));
                }
                TaskType::UpdateDestDisk(index) => {
                    self.action_tx.send(Action::DisplayPopup(
                        popup::Type::Info,
                        String::from("Refreshing disk info"),
                    ))?;

                    // Queue UpdateDiskList for various components
                    self.add(TaskType::Sleep);
                    self.add(TaskType::UpdateDiskList);

                    // Update destination disk ~in-place
                    let disk_list_arc = self.disk_list.clone();
                    self.cur_handle = Some(thread::spawn(move || {
                        let mut disks = disk_list_arc.lock().unwrap();
                        let old_disk = &mut disks[index];
                        disks[index] = disk::refresh_disk_info(old_disk);
                    }));
                }
                TaskType::UpdateDiskList => {
                    let disks = self.disk_list.lock().unwrap();
                    let disks_copy = disks.clone();
                    let action_tx = self.action_tx.clone();
                    self.cur_handle = Some(thread::spawn(move || {
                        if let Err(err) = action_tx.send(Action::UpdateDiskList(disks_copy)) {
                            panic!("Failed to send Action: {err:?}");
                        }
                    }));
                }
            }
            // Done
            self.cur_task.replace(task);
        }
        Ok(())
    }
}

fn parse_bytes_as_str(bytes: Vec<u8>) -> String {
    match String::from_utf8(bytes) {
        Ok(s) => s.trim().to_string(),
        Err(_) => String::from("Failed to parse bytes as UTF-8 text"),
    }
}

fn run_task_command(
    cmd_path: PathBuf,
    cmd_args: Vec<String>,
    task_tx: mpsc::UnboundedSender<TaskResult>,
) -> JoinHandle<()> {
    if cfg!(windows) {
        thread::spawn(move || {
            let result = Command::new(cmd_path)
                .args(cmd_args)
                .stdout(Stdio::piped())
                .output();
            match result {
                Err(e) => {
                    task_tx
                        .send(TaskResult::Error(format!("{:?}", &e)))
                        .expect("Failed to propegate error?");
                }
                Ok(output) => {
                    let stderr = parse_bytes_as_str(output.stderr.clone());
                    let stdout = parse_bytes_as_str(output.stdout.clone());
                    let task_result = TaskResult::Output(stdout, stderr, output.status.success());
                    let err_str = format!("Failed to send TaskResult: {:?}", &task_result);
                    task_tx
                        .send(task_result)
                        .unwrap_or_else(|_| panic!("{}", err_str));
                }
            }
        })
    } else {
        // Simulate task if not running under Windows
        thread::spawn(|| sleep(Duration::from_millis(500)))
    }
}

fn run_task_diskpart(script: &str, task_tx: mpsc::UnboundedSender<TaskResult>) -> JoinHandle<()> {
    if cfg!(windows) {
        let script = script.to_owned();
        thread::spawn(move || {
            let output = diskpart::run_script_raw(&script);
            let stderr = parse_bytes_as_str(output.stderr.clone());
            let stdout = parse_bytes_as_str(output.stdout.clone());
            let task_result = TaskResult::Output(stdout, stderr, output.status.success());
            let err_str = format!("Failed to send TaskResult: {:?}", &task_result);
            task_tx
                .send(task_result)
                .unwrap_or_else(|_| panic!("{}", err_str));
        })
    } else {
        // Simulate task if not running under Windows
        thread::spawn(|| sleep(Duration::from_millis(250)))
    }
}

fn test_paths(
    path_list: Vec<PathBuf>,
    task_tx: mpsc::UnboundedSender<TaskResult>,
) -> JoinHandle<()> {
    thread::spawn(move || {
        let mut missing_paths = Vec::new();
        let task_result: TaskResult;
        path_list.iter().for_each(|path| {
            if !path.exists() {
                missing_paths.push(String::from(path.to_string_lossy()));
            }
        });

        if missing_paths.is_empty() {
            // No missing paths
            task_result = TaskResult::Output(String::from("OK"), String::new(), true);
        } else {
            task_result = TaskResult::Output(
                String::from("Missing item(s)"),
                missing_paths.join(",\n"),
                false,
            );
        };

        let err_str = format!("Failed to send TaskResult: {:?}", &task_result);
        task_tx
            .send(task_result)
            .unwrap_or_else(|_| panic!("{}", err_str));
    })
}